Field of the Invention
The present invention is directed generally to communication outlets and methods for reducing crosstalk therein.
Description of the Related Art
FIGS. 1A-1C depict a conventional high-speed compensation circuit 12 formed on a flexible printed circuit board (PCB) 14 (see FIGS. 1A and 1C). The flexible PCB 14 has been omitted in FIG. 1B to provide a better view of the components of the compensation circuit 12. The compensation circuit 12 was developed for speeds above those specified for the Category 6a standard.
Referring to FIGS. 1A and 1C, the flexible PCB 14 has a first side 15 (see FIG. 1A) opposite a second side 16 (see FIG. 1C). Referring to FIGS. 1B and 1C, the compensation circuit 12 includes six electrically conductive pads P2-P7 configured to contact corresponding tines (or contacts) within a conventional communication outlet or jack constructed in accordance with the RJ-45 standard. The tines are conventionally numbered 1-8 and arranged in four pairs. The first pair includes tines 4 and 5, the second pair includes tines 1 and 2, the third pair includes tines 3 and 6, and the fourth pair includes tines 7 and 8. Each pair conveys a differential signal. The pads P2-P7 are typically soldered to the tines 2-7, respectively.
Referring to FIGS. 1A and 1B, the compensation circuit 12 includes capacitor plates CP3 and CP6 formed on the first side 15 of the flexible PCB 14. The capacitor plates CP3 and CP6 are electrically connected to the pads P3 and P6, respectively. Referring to FIGS. 1B and 1C, the compensation circuit 12 includes capacitor plates CP2, CP4, CP5, and CP7 formed on the second side 16 of the flexible PCB 14. The capacitor plates CP2, CP4, CP5, and CP7 are electrically connected to the pads P2, P4, P5, and P7, respectively.
Referring to FIG. 1B, the capacitor plate CP3 is juxtaposed across the flexible PCB 14 (see FIGS. 1A and 1C) with both the capacitor plates CP5 and CP7. The capacitor plate CP6 is juxtaposed across the flexible PCB 14 (see FIGS. 1A and 1C) with both the capacitor plates CP2 and CP4.
The differential signal carried by the third (split) pair of tines (i.e., the tines 3 and 6) can be thought of as a sine wave that travels along and between the tines. In reality, the signal is much more complex, but mathematically, the signal can be broken down into a superimposed set of sine waves. Thus, wherever the potential is high on one of the tines of the split pair, the potential is low at a corresponding point on the other tine, and vice versa.
As the tines 3 and 6 of the third (split) pair carry the signal down their lengths, they also radiate a signal to neighboring tines. The radiated signal is noise (referred to as crosstalk) that obscures the signals that are propagating along the first pair of tines (tines 4 and 5), the second pair of tines (tines 1 and 2), and the fourth pair of tines (tines 7 and 8).
The compensation circuit 12 counteracts crosstalk, especially the crosstalk radiating from the third split pair. The tine 6 radiates its signal particularly strongly to neighboring tines 5 and 7. Inside the compensation circuit 12, some of the signal received by the pad P3 (which was received from the tine 3 and is opposite the signal conducted by the tine 6) is conducted to the capacitor plate CP3 juxtaposed with the capacitor plates CP5 and CP7, which are connected to the pads P5 and P7 (and therefore, the tines 5 and 7), respectively. The electrical field of an electrical potential applied to the capacitor plate CP3 radiates across a gap between the capacitor plate CP3 and the capacitor plate CP5 and across a gap between the capacitor plate CP3 and the capacitor plate CP7. In this manner, cross talk from the tine 6 is counterbalanced or canceled by anti-crosstalk from the tine 3.
Similarly, the tine 3 radiates its signal particularly strongly to neighboring tines 2 and 4. Inside the compensation circuit 12, some of the signal received by the pad P6 (which was received from the tine 6 and is opposite the signal conducted by the tine 3) is conducted to the capacitor plate CP6 juxtaposed with the capacitor plates CP2 and CP4, which are connected to the pads P2 and P4 (and therefore, the tines 2 and 4), respectively. The electrical field of an electrical potential applied to the capacitor plate CP6 radiates across a gap between the capacitor plate CP6 and the capacitor plate CP2 and across a gap between the capacitor plate CP6 and the capacitor plate CP4. In this manner, cross talk from the tine 3 is counterbalanced or canceled by anti-crosstalk from the tine 6.
Unfortunately, a capacitive structure like that of the compensation circuit 12 may look or function like a low impedance circuit to a high frequency signal. The impedance drops as the size of the capacitive plates CP2-CP7 increase, which increases insertion loss. Therefore, a need exists for communication outlets configured to conduct high speed signals that provide adequate crosstalk compensation. Communication outlets with acceptable insertion loss are particularly desirable. The present application provides these and other advantages as will be apparent from the following detailed description and accompanying figures.